The present invention relates to exhaust treatment devices. More particularly, the present invention relates to an exhaust treatment device with an exhaust gas sensor.
Oxygen gas sensors or exhaust gas sensors have been used in vehicles to sense the presence of constituents (e.g., oxygen, hydrocarbons, nitrous oxides, etc.) in an exhaust gas flow and to sense and/or signal, for example, when an internal combustion engine switches from rich to lean or lean to rich operation or when a catalyst of the exhaust treatment device is no longer operating within a desired range.
Because exhaust gas sensors are required to be positioned within an exhaust gas flow, the exhaust gas sensor is usually mounted to a portion of the exhaust system. Furthermore and due to application requirements, the exhaust system itself will have unique exterior configurations, which may not be optimal mounting locations for exhaust sensors (e.g., irregular welding surfaces). Accordingly, exhaust system designs limit the positioning and configuration of the gas sensor within the exhaust system. For example and in one application, a prefabricated mounting boss is secured to the exhaust system by an attachment method wherein the boss is inserted into or about a hole pierced in an end cone of the exhaust system and the boss is welded to the end cone using metal inert gas (MIG) welding or projection welding. In addition, the exhaust treatment device will typically have insulated catalyst bricks that are disposed within the housing. The catalyst bricks are wrapped in an insulative blanket (mat) disposed between the exterior of the catalyst brick and the interior surface of the exhaust treatment device. In addition, it is also desirable to monitor the gases flowing through the catalyst bricks and to monitor the gas composition between the bricks. However, this requires a sufficient amount of free space between the bricks for the sensing element of the gas sensor to be mounted within the flow path of and between the catalyst bricks (e.g., mid-stream mounting).
Accordingly, it is desirable to provide a catalytic converter with a gas sensor mounted within the catalyst bricks in order to monitor the gases flowing therethrough.